The present invention is directed to writing gratings or other structures in a photosensitve optical waveguide. The creation of a grating utilizing the interference pattern from two interfering coherent UV beams is well known. This technique for construction of Bragg gratings is fully described in U.S. Pat. No. 4,725,110 issued to W H Glenn et al and U.S. Pat. No. 4,807,950 issued to W H Glenn et al.
Bragg grating structures have become increasingly useful and the demand for longer and longer grating structures having higher and higher quality properties has lead to the general need to create improved grating structures.